That bit has always surprised me. It's like he's completely unaware that this is unusual or would make Betsy uncomfortable. It's like he hasn't been properly socialized or has lived in complete isolation all his life, but that obviously hasn't been the case (?). There are aspects of the film that don't make a lot of psychological sense, which (thankfully probably) makes it difficult to reduce the film to psychological analysis.

The porn watching is an interesting detail. There are a few ways to understand it. The common explanation is that Travis is seeking images and instances of human connection, but because he doesn't understand human connection, he seeks it in inappropriate but ubiquitous forms, and then sits there uncomprehending.

But why doesn't he seek it in romances or old melodramas or daytime soaps? Does he have no childhood memories of media that offered romance and connection that he could idolize and retreat to? Why, when he does fantasize, are the fantasies not of escape but of violent confrontation with the world he loathes? Travis does not avoid seeing and experiencing what is distasteful. He conceives of purity, but never tries to escape to some vision of it.

On some level he must feel, regarding the porn, 'this is what people like; I should like it too, shouldn't I?' He thinks of his surroundings as filth, yet he locates normalizing behaviours in it.

On another level, he is attracted to porn--maybe not in uncomplicated sexual gratification, but there is a fascination that keeps him coming back, and not just for some anthropological reason. If the porn were truly repulsive it would've driven it away, and we can assume it does indeed offend his catholic sensibilities. And yet it keeps pulling him back; he even wants to share it with Betsy, and who knows how true his explanation to her is. Travis finds what he loathes fascinating. His interest in porn may not be some misplaced, lonely purity as it's often read. Porn is part of how he engages people, relationships, and the world.

The question remains for me as to why Travis would not be aware that Betsy would find it appropriate.

When Betsy realizes where he's taking her and says, "You've got to be kidding - this is a dirty movie", he answers by saying "No, no" and that he sees all kinds of couples going there. (video of the scene here.) This goes to Mr Sausage's analysis, but it also tells me it's not just about porn being in vogue and that he's in some ways socially clueless.

The question remains for me as to why Travis would not be aware that Betsy would find it appropriate.

When Betsy realizes where he's taking her and says, "You've got to be kidding - this is a dirty movie", he answers by saying "No, no" and that he sees all kinds of couples going there. (video of the scene here.) This goes to Mr Sausage's analysis, but it also tells me it's not just about porn being in vogue and that he's in some ways socially clueless.

Because he really is that clueless.

I think of it like this. Here's a man so divorced from everyone else he really thinks that taking a woman he recently asked out at a politician's campaign office will enjoy seeing pornography in a theater with other people. It would have been far less realistic for Betsy to have thought this was arousing or even amusing. But that's the world Travis lives in. He really thinks this is something people casually do on dates. I understand being awkward as I'm awkward myself but who the hell would take someone to a porno on the first date? And that again, I reiterate is the point. Travis REALLY thinks this is okay.